There is known an image forming apparatus such as an electrophotographic copying apparatus, a facsimile or the like of the electrostatic type in which an electrostatic latent image formed on the surface of a photosensitive drum is converted into a toner image, which is then transferred to paper. As such an image forming apparatus, there is proposed a very small-size apparatus of the so-called portable type (for example, Japanese Patent Publication 17453/1990).
An image forming apparatus of the type above-mentioned comprises a variety of functional components respectively forming:
optical means for illuminating a document and for guiding light reflected from the document;
image forming means for forming an electrostatic latent image on a photoreceptor by the reflected light guided from the optical means, for converting the electrostatic latent image into a toner image and for transferring the toner image to paper;
paper delivery means including a fixing unit for fixing the toner image transferred to the paper, the paper delivery means being adapted to introduce paper into the main body of the apparatus and for discharging the paper from the main body after the paper has been fed to the image forming means;
drive means for driving the means above-mentioned; and
electric components.
The functional components are attached to metallic reinforcing frames such as a pair of lateral plates, stays for connecting the lateral plates to each other, or the like, disposed in a box-like casing formed by a resin molded body.
To spread the image forming apparatus having the arrangement above-mentioned for family and personal uses, it is desired to minimize the sizes and weight of such apparatus with the production and sales costs reduced. However, the conventional image forming apparatus requires reinforcing frames to which the functional components are attached. This accordingly increases the number of component elements, failing to make an economical apparatus in a compact and lightweight design. Further, extra steps of assembling the reinforcing frames are required, thus further increasing the production cost.
When the apparatus is made in a compact and lightweight design, the apparatus can be optionally carried by anybody. This increases the likelihood that the apparatus may be struck or let fall so that an excessive shock is exerted thereto. If an excessive shock is exerted to the apparatus, the apparatus is liable to present, particularly at the joint parts of the apparatus body with the reinforcing frames, breakages such as cracks, plastic deformation and the like due to the difference in material nature and strength between the apparatus body and the reinforcing frames.
In an electrophotographic copying apparatus, there are available two types of document delivery systems, i.e., a so-called document-rack-movable type in which a document rack on which a document is placed is moved to deliver the document, and a so-called roller-delivery type in which a document as held by and between a pair of upper and lower rollers is delivered. In the former type, it is required to dispose, on the top of the apparatus body, a document rack having a size large enough for a document that is placed on the document rack. This inevitably requires, as the plane area for installing the apparatus, a space greater than the sizes of a document. Accordingly, the sizes of the apparatus cannot be minimized as desired. Further, if the document rack under movement comes in contact with an obstacle, the apparatus is liable to become defective in operation and cause troubles. In order to avoid the problems above-mentioned, it is required to securely provide a document-rack moving space around the apparatus. Thus, the apparatus is restricted by requiring a large installation place.
In the roller-delivery type, the length of the document delivery means along the document delivery direction can be made shorter than the length of a document. Accordingly, the main body of the apparatus can be reduced in plane area and consequently made smaller than that of the document-rack-movable type. Even though a document under delivery comes in contact with an obstacle, the document itself is suitably resiliently deformed, enabling the document to be continuously delivered along the obstacle. Thus, as to the space around the apparatus, requirements as strict as those for an apparatus of the document-rack-movable type are not imposed on an apparatus of the roller-delivery type. Accordingly, the apparatus of the roller-delivery type can be used in a relatively narrow space as compared with the apparatus of the document-rack-movable type. Further, even though the apparatus of the roller-delivery type is used in a limited space, neither defective operation nor trouble is anticipated.
In the apparatus of the roller-delivery type, the lower delivery rollers are required to be disposed inside of the main body of the apparatus. However, since the reinforcing frames such as lateral plates, stays and the like are disposed in the main body of the apparatus, the available free space is very small. It is therefore difficult to ensure a space in which the delivery rollers are disposed. When the apparatus body is increased in sizes, the delivery rollers can be readily disposed therein. However, this does not satisfy the demand for a smaller apparatus.
In this connection, it may be proposed to eliminate the reinforcing frames. In this case, however, the main body of the apparatus is reduced in rigidity. This may cause trouble of the influence of an external force upon the functional components, that has not been a problem in a conventional structure. In particular, an image forming apparatus in a compact and lightweight design has been developed based on a concept for spreading such apparatus for family and personal uses. In this connection, the maintenance of apparatus is managed by the user himself or herself, instead of by professional service personnel. However, if the functional components become functionally defective by an external force, the user unfamiliar with technology cannot practically manage such trouble. In this point of view, it is essential in a portable-type image forming apparatus to eliminate the influence of an external force upon the functional components.
To spread the apparatus for family and personal uses, high safety is also required. In particular, provision should be made so as to prevent the user lacking electric knowledge from suffering an accident of electric shock due to his or her careless contact with the wiring or the like in the apparatus, when the main body of the apparatus is opened to cause the inside thereof to be exposed.
Then, it may be proposed to dispose a safety switch adapted to intercept the supply of electric power from the power source line when the main body of the apparatus is opened to cause the inside thereof to be exposed. However, there are instances where the safety switch remains pushed by the hand of the user or the contact of the safety switch is burnt out. In such cases, the accident of electric shock cannot be prevented. Further, when the safety switch is disposed, the number of component elements is increased, resulting in-increased in production cost.